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H Ohkuma

Publications and source records attributed to H Ohkuma.

At least 19 recordsLinked to original sources
PubMed2006

Differential cross section and photon-beam asymmetry for the gamma n --> K+ Sigma- reaction at E gamma = 1.5-2.4 GeV.

Differential cross sections and photon-beam asymmetries have been measured for the gamma n --> K+ Sigma- and gamma p --> K+Sigma0 reactions separately using liquid deuterium and hydrogen targets with incident linearly polarized photon beams of E gamma = 1.5-2.4 GeV at 0.6 < cos ThetacmK< 1. The cross section ratio of sigma K+ Sigma-/sigma K+ Sigma0, expected to be 2 on the basis of the isospin 1/2 exchange, is found to be close to 1. For the K+ Sigma- reaction, large positive asymmetries are observed, indicating the dominance of K* exchange. The large difference between the asymmetries for the K+ Sigma- and K+ Sigma0 reactions cannot be explained by simple theoretical considerations based on Regge model calculations.

Journal Article↗
PubMed2005

Near-threshold diffractive psi-meson photoproduction from the proton.

Photoproduction of a phi meson on protons was studied by means of linearly polarized photons at forward angles in the low-energy region from threshold to Egamma = 2.37 GeV. The differential cross sections at t = -|t|min do not increase smoothly as Egamma increases but show a local maximum at around 2.0 GeV. The angular distributions demonstrate that phi mesons are photoproduced predominantly by helicity-conserving processes, and the local maximum is not likely due to unnatural-parity processes.

Journal Article↗
PubMed2004

Displacement of central sulcus in cerebral arteriovenous malformation situated in the peri-motor cortex as assessed by magnetoencephalographic study.

BACKGROUND: Intra-operative monitoring of the position of the central sulcus (CS) is indispensable to properly treat a peri-motor cortex lesion. Noninvasive preoperative studies for identification of CS are also needed for choosing the optimal operative procedure. Magneto-encephalography (MEG) has recently been introduced for non-invasive preoperative investigation and cortical functional mapping. METHODS: Stereotactic mapping of functional CS anatomy was performed preoperatively on 13 subjects using somatosensory evoked fields with MRI-linked whole head MEG system. All subjects had a left sided peri-motor cortex lesion with diagnoses including the following conditions: three arteriovenous malformations (AVM), seven gliomas, three meningiomas. FINDINGS: Functional CS in supratentorial brain tumor and parietal AVM cases corresponded with anatomical CS identified by MRI. But the AVM cases in whom the nidus was situated within the peri-motor cortex showed discrepancies between anatomical CS and functional CS. INTERPRETATION: Careful consideration of the operative procedure combined with non-invasive cortical functional mapping is needed to optimally treat AVM and congenital brain lesions situated in the anatomical peri-motor cortex.

Adolescent↗
PubMed2003

Beam-polarization asymmetries for the p(gamma-->, K+)Lambda and p(gamma-->, K+)Sigma(0) reactions for E(gamma)=1.5-2.4 GeV.

Beam polarization asymmetries for the p(gamma-->,K+)Lambda and p(gamma-->,K+)Sigma(0) reactions are measured for the first time for E(gamma)=1.5-2.4 GeV and 0.6<cos((theta(c.m.)(K+))<1.0 by using linearly polarized photons at the Laser-Electron-Photon facility at SPring-8 (LEPS). The observed asymmetries are positive and gradually increase with rising photon energy. The data are not consistent with theoretical predictions based on tree-level effective-Lagrangian approaches. Including the new results in the development of the models is, therefore, crucial for understanding the reaction mechanism and to test the presence of baryon resonances which are predicted in quark models but are thus far undiscovered.

Journal Article↗
PubMed2003

Evidence for a narrow S = +1 baryon resonance in photoproduction from the neutron.

The gamman-->K(+)K(-)n reaction on 12C has been studied by measuring both K+ and K- at forward angles. A sharp baryon resonance peak was observed at 1.54+/-0.01 GeV/c(2) with a width smaller than 25 MeV/c(2) and a Gaussian significance of 4.6sigma. The strangeness quantum number (S) of the baryon resonance is +1. It can be interpreted as a molecular meson-baryon resonance or alternatively as an exotic five-quark state (uuddsmacr;) that decays into a K+ and a neutron. The resonance is consistent with the lowest member of an antidecuplet of baryons predicted by the chiral soliton model.

Journal Article↗
PubMed2003

Dissecting aneurysms of the middle cerebral artery: neuroradiological and clinical features.

There are few reported cases of nontraumatic dissecting aneurysms of the middle cerebral artery (MCA), and their neuroradiological and clinical features have not been analysed. We looked at these aspects in a collaborative study. We reviewed 13 patients diagnosed as having a dissecting aneurysm of the MCA based on clinical signs and neuroradiological findings in 46 stroke centres between 1995 and 1999. There were four patients who presented with cerebral ischaemia, and nine who presented with bleeding. Of the former group, three were aged less than 15 years. Cerebral angiography showed extensive stenosis and a double lumen of the M1 portion in all four patients. High signal on T1-weighted images around the arterial flow void, due to intramural haematoma, was often seen in the second week. MR angiography showed findings corresponding those of intra-arterial angiography in all four cases. We saw an infarct on CT or MRI in territory of the perforating branches of the M1 segment in all four patients. In the patients presenting with bleeding, pure subarachnoid haemorrhage or a sylvian fissure haematoma was seen on initial CT, and the predominant angiographic finding was dilatation with stenosis, but the site of the lesions was not uniform. A double lumen or intimal flap was seen in about half the cases. Rebleeding occurred within 14 days of the onset in five of the nine patients, with a poor prognosis.

Adolescent↗
PubMed2003

Neuroendoscopic surgery for intracerebral haemorrhage--comparison with traditional therapies.

Endoscopy is a new therapeutic option for hypertensive intracerebral haemorrhage. Although it has the advantages of being less invasive than craniotomy and more effective than conservative treatment, not all patients are candidates for it. Since it is important to clarify which characteristics of patients are indications for this operation, we retrospectively evaluated the role of endoscopic surgery in comparison with traditional treatments for hypertensive intracerebral haemorrhage. Seven patients were treated with endoscopic surgery in our institution between January 2000 and November 2001. Two had thalamic haemorrhage, 4 putaminal haemorrhage, and 1 intracerebral haemorrhage. The average age of patients was 55 years. Endoscopic operation was mainly selected for haematomas more than 20 ml and less than 40 ml in volume. Generally, endoscopy yielded good outcomes with GR in 50 % of patients. Adequate indications for endoscopic operation may be the following; 1) Putaminal haematoma of small-intermediate size, 2) Haematoma situated deep in the brain, e. g., thalamic haemorrhage, 3) Intraventricular haematoma, 4) High-risk patients who cannot tolerate general anaesthesia.

Adult↗
PubMed2002

Development of a highly sensitive enzyme-linked immunosorbent assay for bisphenol A in serum.

4,4'-Isopropylidenediphenol, bisphenol A (BPA), was derivatized to BPA-carboxymethylether (BPA-CME), BPA-carboxypropylether (BPA-CPE) and BPA-carboxybutylether (BPA-CBE), and then linked to bovine serum albumin (BSA). The BPA-BSA conjugates were injected into female New Zealand White rabbits, which then generated six kinds of polyclonal antibodies. In addition, BPA and bisphenol B (BPB)-enzyme conjugates were derivatized to BPA-CME, BPA-CPE, BPA-CBE, BPA-carboxyphenylether (CPhE) and BPB-CPE, and then linked to horseradish peroxidase (HRP). An enzyme-linked immunosorbent assay (ELISA) was developed and the specificity of the antibodies was confirmed by comparison with pre-immune serum and by competitive assays using different dilutions of BPA standards. Although anti-BPA antibodies cross-reacted with BPB by more than 13.6% at all dilutions used, cross-reaction with phthalates and phenols occurred only less than 0.1%. The combination with the highest sensitivity was obtained using anti-BPA-CME-BSA antibody and BPA-CPhE-HRP conjugate. ELISA successfully detected BPA in human serum at concentrations as low as 0.3 ng mL(-1), and over a measurable range of 0.3-100 ng mL(-1). Recovery tests were carried out by adding BPA to three kinds of human serum, and ranged from 89.7 to 97.3%, from 85.4 to 94.9% and from 81.9 to 97.4%, respectively. The correlation between the results from ELISA and gas chromatography-mass spectrometry (GC-MS) for BPA in spiked serum was r2 = 0.990, indicating that the proposed method is a potential tool for screening a large number of human serum samples.

Animals↗
PubMed2001

Changes of beta-actin mRNA expression in canine vasospastic basilar artery after experimental subarachnoid hemorrhage.

The aim of this study was to investigate whether vascular remodeling occurs during cerebral vasospasm after subarachnoid hemorrhage (SAH). Beta-actin mRNA expression and structural change of its 3' untranslated region (UTR) which are considered a non-specific marker for vascular remodeling, were examined by Northern analysis and polymerase chain reaction analysis in a canine basilar artery after experimental SAH. The changes in the area of tunica media in the basilar artery were also examined histopathologically. Increased beta-actin mRNA expression and its structural changes of 3' UTR in the vasospastic basilar artery were markedly seen 7 and 14 days after SAH accompanied by increased area of tunica media in the basilar artery. The results suggest that vascular remodeling occurs and takes part in the luminal narrowing during cerebral vasospasm.

3' Untranslated Regions↗
PubMed2001

Incidence and significance of early aneurysmal rebleeding before neurosurgical or neurological management.

BACKGROUND AND PURPOSE: Rebleeding is a major cause of death and disability in aneurysmal subarachnoid hemorrhage (SAH); however, there has been no report focusing on rebleeding before hospitalization in neurosurgical or neurological institutions. The aim of this study was to clarify the incidence of prehospitalization rebleeding, its impact on the clinical course and prognosis in patients with aneurysmal SAH, and the possible factors inducing it. METHODS: In 273 patients who were admitted to our institution within 24 hours after the initial SAH bleeding and whose clinical course before admission could be fully evaluated, the patients' clinical conditions and CT findings on admission, operability, prognosis, and possible factors inducing rebleeding were comparatively evaluated between the patients with and without an episode of prehospitalization rebleeding. RESULTS: Of the 273 patients, 37 (13.6%) patients suffered from 39 episodes of rebleeding in the ambulance or at the referring hospital before admission to our hospital. The peak time of rebleeding was within 2 hours (77%), in which the incidence was statistically significant compared with that occurring 2 to 8 hours after the initial SAH bleeding (P<0.01). The group experiencing rebleeding showed more severe Hunt and Hess grades on admission, higher rates of intracerebral hematoma, of intraventricular hematoma, and of subdural hematoma on CT scan on admission, less operability, and poorer prognoses with statistically significant differences compared with the group that did not experience rebleeding. Systolic arterial pressure >160 mm Hg was a possible risk factor of rebleeding (odds ratio 3.1, 95% CI 1.5 to 6.8). CONCLUSIONS: Rebleeding during transfer and at the referring hospital is not rare. To improve overall outcome of aneurysmal SAH, the results obtained in this study should be made available to general practitioners and the doctors devoted to emergency medicine.

Blood Pressure↗
PubMed2001

[A case report of mirror writing with low perfusion of bilateral anterior cerebral arteries].

A 20-year-old female experienced temporary unintentional mirror writing associated with low perfusion of the bilateral anterior cerebral arteries. When she was 17 years old, she had developed multiple idiopathic intracerebral hemorrhages and right hemiparesis. At the age of 20, she had a generalized convulsion for which she was transferred to our department. Computed tomography (CT) and magnetic resonance images of the brain were obtained, but no fresh abnormal lesion could be detected. The following day, after she had recovered from postictal symptoms, she wrote mirror image words, and her mirror writing then gradually improved within one week. Single photon emission CT showed low perfusion of both anterior cerebral arteries. We concluded that bilateral vascular insufficiency to the supplementary motor areas and corpus callosum caused mirror writing in this case.

Adult↗
PubMed2001

[Pharmaceutical evaluation of fast-disintegrant tablet containing nicorandil-loaded particles].

AIM: To improve the bioavailability and taste of fast-disintegrating tablet (FD tablet) containing nicorandil-loaded particles. METHODS: A FD tablet containing nicorandil-loaded particles with 1%-4% croscarmellose sodium in addition of D-mannitol and lactose (9:1) was prepared and the dissolution and absorption characteristics were examined, in comparison with FD tablet and commercial tablets of nicorandil. In vivo absorption of nicorandil from FD tablet was evaluated in beagle dogs. RESULTS: The disintegration time of FD tablets containing 1% croscarmellose sodium with 6 mm and 10 mm in diameter were about 12 and 23 seconds, respectively. When nicorandil-loaded particles consist of myristyl alcohol and stearyl alcohol were put in FD tablet, nicorandil release from FD tablet continued until 6 h while nicorandil release from Sigmart and FD tablet containing nicorandil crystals finished within 5 min. In vivo absorption of nicorandil from Sigmart and FD tablet containing nicorandil crystals was very similar after oral administration in beagle dogs and no statistic difference in AUC, Tmax, Cmax was observed between these tablets. However pharmacokinetics parameters of nicorandil after oral administration of FD tablet containing nicorandil-loaded particles showed that nicorandil was delivered into the body at a suitable absorption rate with similar AUC, delayed Tmax and lower Cmax. CONCLUSION: The reports suggest that the modification of properties of myristyl alcohol and stearyl alcohol released from the drug-loaded particles system would lead to more acceptable bioavailability of the system. However, The formulation of particles and may have a masking effect against the bitter taste and irritation of the drug.

Administration, Oral↗
PubMed2000

Role of 123I-IMP SPET in the early diagnosis of borderline chronic hydrocephalus after aneurysmal subarachnoid haemorrhage.

Chronic hydrocephalus after aneurysmal sub-arachnoid haemorrhage (SAH) is easily diagnosed in most cases. However, the diagnosis is sometimes difficult in borderline cases, in which (a) pathognomonic clinical deterioration due to hydrocephalus is masked by the neurological deficits caused in the acute stage of SAH and (b) ventricular enlargement is not so marked on CT scan. The purpose of this study was to investigate whether or not iodine-123 labelled N-isopropyl-p-iodo-amphetamine (123I-IMP) single-photon emission tomography (SPET) is of value for the early diagnosis of borderline chronic hydrocephalus after SAH. Fifteen patients who met the criteria of borderline chronic hydrocephalus were selected for the study, and underwent a shunt operation. The patients were divided into a shunt-effective group and a shunt-ineffective group according to neurological improvement after the shunt operation. 123I-IMP SPET was performed in the acute stage of SAH, within 1 week before the shunt operation, and 2 weeks after the shunt operation. Regional cerebral blood flow was estimated by the 123I-IMP autoradiographic method. Pre-shunting periventricular low-perfusion areas showed statistically significant differences between the two groups (P<0.05). In the shunt-effective group, peri-ventricular low-perfusion areas on pre-shunting SPET were significantly enlarged compared with those in the acute stage of SAH (P<0.05), and they were significantly reduced after the shunt operation (P<0.05). In the shunt-ineffective group, periventricular low-perfusion areas showed no significant changes during the course. These results suggest that periventricular low-perfusion areas enlarge in the early stage of chronic hydrocephalus after SAH, and that 123I-IMP SPET can be used for both the early diagnosis of borderline chronic hydrocephalus after SAH and the prediction of shunt effectiveness.

Aged↗
PubMed2000

Uveal effusion syndrome: clinical features, surgical treatment, histologic examination of the sclera, and pathophysiology.

PURPOSE: To clarify clinical features and pathophysiology and to evaluate surgical outcome of subscleral sclerectomy for primary uveal effusion syndrome. DESIGN: Prospective, consecutive noncomparative case series. PARTICIPANTS: Nineteen eyes of 16 patients diagnosed with uveal effusion syndrome treated in our clinic between 1989 and 1998. METHODS: Patients were examined by routine ophthalmologic examinations, fluorescein and indocyanine green angiography; measurement of the axial length of the eyeball; magnetic resonance imaging; and echography. Subscleral sclerectomy (sclerectomy under the scleral flap) was performed at the equator on all patients. Histologic examination of excised sclera was carried out on all samples. Patients were followed for outcome over time. MAIN OUTCOME MEASURES: Reattachment of the choroid and retina with resolution of the serous fluid. RESULTS: Three subgroups were identified: In type 1, nanophthalmic eye; the eyeball is small (average axial length 16 mm) and high hypermetropic (average +16 diopters); in type 2, the eyeball size is normal (average axial length 21 mm) with small refractive error; and in type 3, the eyeball size is normal. Histologically, types 1 and 2 demonstrated abnormal sclera with disorganization of collagen fiber bundles and deposits of proteoglycans in the matrix, whereas type 3 showed normal sclera. Subscleral sclerectomy was effective for types 1 and 2, inducing postoperative resolution of the subretinal fluid. However, type 3 eyes were not helped by this technique. CONCLUSIONS: Primary uveal effusion syndrome is caused by abnormalities of the sclera and increased resistance to transscleral fluid outflow as subscleral sclerectomy is an effective treatment in types 1 and 2 only, correct preoperative classification is essential for early surgical management.

Adult↗
PubMed2000

Impact of cerebral microcirculatory changes on cerebral blood flow during cerebral vasospasm after aneurysmal subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Cerebral microcirculatory changes during cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH) are still controversial and uncertain. The aim of this study was to investigate the changes of cerebral microcirculation during cerebral vasospasm and to clarify the roles of microcirculatory disturbances in cerebral ischemia by measuring cerebral circulation time (CCT) and regional cerebral blood flow (rCBF). METHODS: In 24 cases with aneurysmal SAH, rCBF studies by single-photon emission CT and digital subtraction angiography (DSA) were performed on the same day between 5 and 7 days after SAH and/or within 4 hours after the onset of delayed ischemic neurological deficits. CCT was obtained by analyzing the time-density curve of the contrast media on DSA images and was divided into proximal CCT, which was the circulation time through the extraparenchymal large arteries, and peripheral CCT, which was the circulation time through the intraparenchymal small vessels. They were analyzed in association with rCBF and angiographic vasospasm. RESULTS: Severe angiographic vasospasm statistically decreased rCBF, and correlation between the degree of angiographic vasospasm and rCBF was seen (r=0.429, P=0.0006). Peripheral CCT showed strong inverse correlation with rCBF (r=-0.767, P<0.0001). Even in none/mild or moderate angiographic vasospasm, prolonged peripheral CCT was clearly associated with decreased rCBF. CONCLUSIONS: In addition to the marked luminal narrowing of large arteries detected as severe angiographic vasospasm, microcirculatory changes detected as prolonged peripheral CCT affected cerebral ischemia during cerebral vasospasm. These results suggested that impaired autoregulatory vasodilation or decreased luminal caliber in intraparenchymal vessels may take part in cerebral ischemia during cerebral vasospasm.

Adult↗
PubMed2000

[A case of delayed subrachnoid hemorrhage from vertebrobasilar artery dissecting aneurysm].

We report a case of delayed subarachnoid hemorrhage (SAH) from a vertebrobasilar artery dissecting aneurysm (VBA-DA). The patient was a healthy 32-year-old woman with a sudden onset of severe occipitalgia. Next day, her headache improved gradually, and she consulted with our department. Although we initially suspected that she was suffering from SAH, neurological findings, CT, and cerebrospinal fluid examination did not reveal any abnormal conditions, including SAH. Therefore, she was treated conservatively with analgesics. Twelve days after the initial onset of the headache, she was admitted because of severe re-attack of headache, rt. hemiparesis with rt. oculomotor nerve palsy and loss of consciousness. CT revealed moderate SAH and cerebral angiograms showed VBA-DA. After the cerebral angiography, bleeding reoccurred two times and she lost her life. We present the case, review the literature and discuss the relationship between presenting symptom of headache and non-hemorrhagic VBA-DA. A few cases of non-hemorrhagic VBA-DA have been reported in the literature in which the only presenting symptom was headache, followed by delayed SAH from non-hemorrhagic dissecting aneurysm. Consequently, we concluded that her initial symptom of headache was due to dissection of vertebrobasilar artery, and that SAH was due to delayed hemorrhage of non-hemorrhagic VBA-DA. Even when neurological findings, CT and cerebrospinal fluid examination reveal no abnormalities in the early stage after the sudden onset of headache, especially in the occiptal or nuchal regions, non-hemorrhagic VBA-DA, which has a risk of fatal hemorrhage, cannot be ruled out with certainty. Therefore, MRI, MRA, three-dimensional CT, or cerebral angiography should be performed in such cases.

Adult↗
PubMed1999

Histological dissociation between intra- and extraparenchymal portion of perforating small arteries after experimental subarachnoid hemorrhage in dogs.

This study was conducted to investigate whether the intraparenchymal and extraparenchymal portions of small cerebral arteries show different histopathological changes after subarachnoid hemorrhage (SAH). SAH was produced in dogs by a two-hemorrhage method, and the dogs were perfusion-fixed at 7 and 14 days after SAH. Normal untreated animals were also examined to determine whether or not the histological and morphological changes in the perforating arteries were affected by the perfusion pressure during perfusion-fixation. Control dogs, which received cisternal injection of saline, and untreated normal dogs, which were divided into two groups depending on the perfusion pressure during perfusion-fixation, were also examined. Microvascular corrosion casts produced by arterial injection of polyester resin were examined by scanning electron microscopy (SEM) with morphometric analysis of the caliber of the small perforating arteries. Slices sectioned parallel to the pontine surface were examined by SEM and by light microscopy with morphometric analysis of the luminal diameter and wall thickness of the small perforating arteries. Corrosion casts showed irregular width with folds in the perforating arteries 7 days after SAH. Sectioned slices showed an increased wall thickness of the perforating arteries with intimal corrugation 7 days after SAH. Morphometric analysis revealed that the extraparenchymal portion of the perforating arteries showed no significant differences between any of the groups tested; however, the intraparenchymal portion showed a significant decrease of luminal diameter 7 days after SAH, and a significant increase of wall thickness 7 and 14 days after SAH. The perfusion pressure during perfusion-fixation did not affect the histological changes in the perforating arteries. The results of this study showed that the vasoconstrictive response of the perforating arteries to SAH was different between the extraparenchymal and the intraparenchymal portion, and showed that the intraparenchymal portion of the perforating arteries constrict after SAH, which may affect cerebral ischemia during cerebral vasospasm by increasing total cerebrovascular resistance.

Animals↗